The infamous sea witch, Circe, causes trouble in pretty much every story she shows up in. (Check out Homer's Odyssey for another example.) She's famous for being sneaky and for almost always using her magic for her own selfish purposes. You'd think Glaucus would know better than to go to the sea witch for a love potion. You'd think he'd totally know not to trust her after he rejects her advances. But nope. Glaucus believes that Circe has given him a legit love potion and inadvertently turns Scylla into a monster. Like in so many other myths, Circe proves herself to be untrustworthy, vindictive, and really bad with rejection.